Southwest:
1. I need to get there on time.
2. I need to get there for less than $1200 roundtrip.
3. I need to rack up the free flights quickly.
4. I change my plans often and don't want to pay any fees to do so.

United:
1. When Southwest doesn't have a nonstop to fit my schedule.

[This message has been edited by Tino (edited 11-06-2000).]